Prognostic and therapeutic interest of a new classification in inferior hip dislocation: a systematic review of the literature.

Introduction: Reported cases of inferior dislocation in the literature are found under several names (inferior, anteroinferior, obturator, or erecta), which may be source of confusion. The purpose of this comprehensive review of the literature is to collect as many cases of inferior dislocation as possible to determine better therapeutic strategies, outcome after reduction, complications, and prognostic factors.

Methods: In April 2020, a literature search was performed in Pubmed, Medline, Scopus, Cochrane, and Embase databases. The MeSH keywords were "OBTURATOR DISLOCATION HIP" or "ANTERIOR DISLOCATION HIP" or "INFERIOR DISLOCATION HIP." Authors independently selected articles that met the selection criteria, with no time limit.

Results: Out of the 97 articles selected, there were 119 cases of primary inferior hip dislocations. This review of the literature has allowed us to differentiate 3 radiographic subtypes of inferior dislocations, which correspond to 3 different anatomical positions of the femoral head: "obturator" dislocation, "proximal anterior-inferior" dislocation, and "distal anterior-inferior" dislocation. Our subtype classification yielded 39 obturator subtype inferior dislocations (32.8%), 66 proximal anteroinferior subtypes (55.4%), and 14 distal anteroinferior (11.8%). The obturator subtype is at risk of reduction failure and femoral neck fracture during the reduction manoeuver.

Conclusions: Our study identified 3 subtypes with different prognosis, with obturator and distal anteroinferior dislocations having a poorer prognosis because of their pre- and post-reduction complications. We were unable to determine the correct manoeuver to reduce inferior dislocations without taking the risk of femoral neck fracture, but each of these subtypes may require a different manoeuver.